The present invention concerns a system for assisting maintenance of a particle filter integrated in an exhaust line of a motor vehicle diesel engine.
Because a particle filter clogs up progressively whenever a vehicle equipped with the filter is in use, one of the main problems linked to the use of a particle filter is maintaining it. The residues that accumulate in it come mainly from four different sources. These residues may consist of metal particles from the engine or the exhaust line or that are not filtered out on the inlet side of the engine. Other residues may take the form of ash from the lubricants used in the engine or the fuel supplied to it. Finally, further residues may take the form of combustion residues of an additive for assisting regeneration. Additives of this kind are known in the art and may be mixed with the fuel supplied to the engine to lower the combustion temperature of soot trapped in the particle filter.
The above four kinds of residue accumulate in a particle filter of a design that uses an additive to assist regeneration by encouraging the combustion of soot. If this kind of additive is not used, for example in the case of impregnated or catalytic particle filters, only three of the above kinds of residue are present in the filter, which reduces the cumulative volume of residues for a given distance traveled.
However, regardless of the design used, the particle filter clogs up progressively, thereby reducing the volume available for storing particles. Because of this, to preserve the thermo-mechanical efficacy of the filter, it must be regenerated more and more frequently, and this is reflected in an increase in the additional fuel consumption associated with the particle filter in the situation where regeneration is effected by post-injection or by using a burner, for example, and by dilution of the engine lubricating oil by the post-injected fuel, with a risk of damaging the engine.
What is more, the reduced space available for storing soot leads to increasingly high head losses through the filter, which is reflected both in an increase in the fuel consumption of the vehicle outside the regeneration phase and in a risk of damaging the engine, for example if the pressure difference across the filter is too high and causes re-opening of the valves. It is therefore necessary to clean or to change the filter after traveling a certain distance, when the volume available for storing particles has become too small.
In current applications in which vehicles are equipped with a particle filter, cleaning is effected at a fixed distance, for example 120 000 kilometers, regardless of how the vehicle is used. Unfortunately, the quantity of residues stored depends on many factors, such as oil consumption, additive consumption, the number of regenerations already attempted, etc.
Two vehicles that have traveled the same distance may have accumulated very different quantities of residues, according to how the vehicles are used. For example, travel in towns with an average fuel consumption of 10 liters per 100 kilometers generates 67% more additive consumption residues than travel on the open road with an average consumption of 6 liters per 100 kilometers. Clearly, by defining a particle filter cleaning period for all vehicles in advance, the degree of clogging of their particle filters is not necessarily optimized, which is reflected in the considerable disparities observed between the degree of clogging of particle filters at the time of cleaning operations.
Moreover, the current climate, with a high demand to impose the use of a particle filter, has particularly highlighted the overall cost of the system and in particular the cost of maintenance, which makes it essential to delay the particle filter cleaning operation as long as possible, to reduce the cost to the user.
It is therefore necessary to optimize the frequency of cleaning the particle filter.